Large capacity tank for storing and transporting low temperature liquids

ABSTRACT

944,748. Storing liquefied gases. CONCH INTERNATIONAL METHANE Ltd. Aug. 13, 1962 [Oct. 6, 1961], No. 30889/62. Addition to 850,204. Heading F4P. In a large liquefied gas, e.g. methane container of quadrilateral horizontal cross-section as claimed in the parent Specification, having its vertical walls 1 stiffened by a plurality of vertically spaced horizontal beams 2 each of which is secured to and extends continuously round the interior of the container and wherein the corner portions of each beam are connected by cross-ties 3, the points of connection divide the beam of each side wall into sections of diminishing length towards the middle of the wall. As shown, each beam 2 is divided into five sections of length ratio 9, 8, 7, 8, 9.

March 9, 1965 LARGE CAPACITY K FOR STORING AND TRANSPORTIN DRE 1', 6

TEMPERAT Filed 00 W. BERGMANN LIQUIDS 1961 7 INVENTOR. Heinrich WBergmann BY WM WMM United States Patent "Ice 3,172,560 LARGE CAPACITY TANK FOR STORING AND TRANSPORTING LOW TEMPERA- TURE LIQUIDS Heinrich W. Bergmann, Norman, 0kla., assignor to Conch International Methane Limited, Nassau, Bahamas, a corporation of the Bahamas Filed Oct. 6, 1961, Ser. No. 143,342 6 Claims. (Cl. 22071) This invention relates to a large capacity tank for storing and transporting a liquid which needs to be maintained at a temperature differing widely from the ambient temperature, in particular for storing and transporting liquefied gases, such as liquefied methane, liquefied natural gas or liquefied nitrogen, at about atmospheric pressure and at low temperature.

A tank has already been proposed (see US. patent specification No. 2,982,441), which is of quadrilateral shape in horizontal cross section and which has a top wall, a bottom wall and vertical side walls, a plurality of horizontally disposed vertically spaced apart reinforcing beams secured to the inner face of each of the vertical side walls and extending continuously about said faces, a plurality of horizontally disposed cross tie members extending between the reinforcing beams of adjacent vertical side walls in spaced relationship with the lines of intersection of said adjacent vertical side walls, the cross tie members being joined at their ends to the reinforcing beams at such points that each of the beams is divided into a number of sections.

Now in order to obtain the most economical utilization of the tank wall material the construction according to the invention differs from the known construction in that the sections adjacent to each line of intersection have the greatest length and that the lengths of the other sections diminish towards the middle part of each vertical side wall of the tank.

The construction according to the invention will now be explained with reference to the drawings in which- FIG. 1 shows a horizontal cross section of the tank according to the invention;

FIG. 2 shows a vertical cross section of the tank according to FIG. 1; and

FIG. 3 shows schematically the deformations that may occur in a tank under symmetric loading.

The tank which is preferably prismatic consists of the vertical side walls 1 and the top and bottom walls 7 and 6. A plurality of horizontally disposed vertically spaced apart reinforcing beams 2 extend continuously about the inner surface of the vertical side walls 1. A plurality of horizontally disposed cross tie members 3 are present between the reinforcing beams 2 of adjacent vertical side walls 1 in spaced relationship with the lines of intersection of said adjacent vertical side walls 1. The cross tie members 3 are joined at their ends to the reinforcing beams 2 at such points that each of the beams 2 is divided into a number of sections a, b, c. Between the lengths of said sections there should be a special relationship as will be explained later. The tank is normally provided with a vent-stack 5 and the top and bottom walls 7 and 6 are normally also provided with suitable reinforcing means (not shown in the drawings).

When the tank is placed horizontally and it is in loaded condition the pressure load is symmetrical about the center bulkhead. In that case the cross tie members 3 are primarily stressed in tension so that the displacements of the points where the cross tie members 3 are connected to the reinforcing beams 2 are small. Each reinforcing beam 2 with a proportionate amount of wall plate can then be conceived as a continuous beam on almost rigid supports. For maximum efficiency under 3,1725% Patented Mar. 9, 1965 this loading condition alone the cross tie members 3 should be connected to the reinforcing beams 2 at equidistant intervals. In other words, in that case the lengths of the sections a, b, 0, should be the same. The resulting deflections of the reinforcing beams 2 stem primarily from elongations of axially loaded members and are small even in the case of high pressure loads. As the stresses in the sections a, b, c, are proportional to the square of their lengths, and as the lengths of a, b and c are the same, the stress distribution is essentially the same in each section. The pattern of deflection of the tank walls under a symmetric pressure load is shown by the dotted lines in FIG. 3.

When the tank is in loaded condition and it is inclined at the same time, an anti-symmetrical loading condition is superimposed on the symmetrical loads. This is, for example, the case when the tank is located on a ship and when the ship is rolling. Under the anti-symmetrical loading condition alone, the elongations of the cross tie members 3 is negligible as compared to the deformations caused by bending of the reinforcing beams 2. The tank walls bow appreciably already under small anti-symmetrical loads, producing high stresses in the center sections, b, c, b.

Upon superimposing the stresses resulting from the symmetrical and the anti-symmetrical loading conditions, relatively low stresses are found at the corners of the tank and rather high stresses at the midspans of the tank walls. Therefore, according to the invention the sections, a, b and c, are so dimensioned that the length of section a is larger than the length of section b and the length of section b is larger than the length of section 0. In other words, the sections adjacent to each line of intersection of adjacent vertical side walls have the greatest length and the length of the other sections diminishes towards the middle part of each vertical side wall.

Then the stresses due to symmetrical loading are high at the corners and low at the midspans; the stresses due to anti-symmetrical loading are low at the corners and high at the midspans. With properly chosen lengths of the sections a, b and c, the superposition of both stress patterns leads to rather uniform stress distribution over the lengths of the tank walls in the more severely loaded half of the tank during the rolling cycle of the ship. For normal design conditions the ratio 918:7 for the lengths of the sections a, b and c, was found to be satisfactory, but other ratios should be used if the number of ties or the conditions are varied.

I claim:

1. A large tank for storing or transporting a liquid which needs to be maintained at a temperature differing widely from the ambient temperature, which tank is of quadrilateral shape in horizontal cross section and has a top wall, a bottom wall and vertical side walls, a plurality of horizontally disposed vertically spaced apart reinforcing beams secured to the inner face of each of the vertical side walls and extending continuously about said faces, a plurality of horizontally disposed cross tie members ex tending between the reinforcing beams of adjacent vertical side walls in spaced relationship with the line of intersection of said adjacent vertical side walls, the cross tie members being joined at their ends to the reinforcing beams at such points that each of the beams is divided into a number of sections, the sections adjacent to each line of intersection having the greatest length and the length of the other sections diminishing towards the middle part of each vertical side wall of the tank.

2. A tank as claimed in claim 1 in which each reinforcing beam is divided in the above mentioned way into five sections, the ratio of the lengths of the sections being 9, 8, 7, 8, 9.

3. A ship provided with a heat insulated hold in which a tank according to claim 1 is located.

4. A tank for storing or transporting a liquid which needs to be maintained at a temperature differing Widely from the ambient temperatureflvhich tank is of quadrilateral shape in horizontal cross section and has a top wall, a bottom wall and vertical side walls, said tank being one of the tanks formed by dividing a larger tank into a number of smaller tanks by means of at least one dividing wall, a plurality of horizontally disposed vertically spaced apart reinforcing beams being secured to the inner face of each of the vertical side walls and extending continuously about said faces, a plurality of horizontally disposed cross tie members extending between the reinforcing beams of adjacent vertical side walls in spaced relationship with the lines of intersection of said adjacent vertical side walls, the cross tiemeinbers being joined at their ends to the reinforcing beams at such points that each of the beams is divided into a number of sections, the sections adjacent to each line of intersection having the greatest length and the length of the other sections diminishing towards the middle part of each vertical side wall of the tank.

5. A tank as claimed in claim 4 in which each reinforcing beam is divided in the above mentioned way into five sections, the ratio of the lengths of the sections being 9, 8, 7, 8, 9.

6. A ship provided with a heat insulated hold in which a tank according to claim 4 is located.

References Cited by the Examiner UNITED STATES PATENTS 2,296,414 9/42 Albrecht 22071 2,982,441 5/61 Farrell et al 220-71 THERON E. CONDON, Primary Examiner. 

1. A LARGE TANK FOR STORING OR TRANSPORTING A LIQUID WHICH NEEDS TO BE MAINTAINED AT A TEMPERATURE DIFFERING WIDELY FROM THE AMBIENT TEMPERATURE, WHICH TANK IS OF QUADRILATERAL SHAPE IN HORIZONTAL CROSS SECTION AND HAS A TOP WALL, A BOTTOM WALL AND VERTICAL SIDE WALLS, A PLURALITY OF HORIZONTALLY DISPOSED VERTIALLY SPACED APART REINFORCING BEAMS SECURED TO THE INNER FACE OF EACH OF THE VERTICAL SIDE WALLS AND EXTENDING CONTINUOUSLY ABOUT SAID FACES, A PLURALITY OF HORIZONTALLY DISPOSED CROSS TIE MEMBERS EXTENDING BETWEEN THE REINFORCING BEAMS OF ADJACENT VERTICAL SIDE WALLS IN SPACED RELATIONSHIP WITH THE LINE OF INTERSECTION OF SAID ADJACENT VERTICAL SIDE WALLS, THE CROSS TIE MEMBERS BEING JOINED AT THEIR ENDS TO THE REINFORCING BEAMS AT SUCH POINTS THAT EACH OF THE BEAMS IS DIVIDED INTO A NUMBER OF SECTIONS, THE SECTIONS ADJACENT TO EACH LINE OF INTERSECTION HAVING THE GREATEST LENGTH AND THE LENGTH OF THE OTHER SECTIONS DIMINISHING TOWARDS THE MIDDLE PART OF EACH VERTICAL SIDE WALL OF THE TANK. 